Fuel fired burners are desirable for reliable regeneration of diesel particulate filters (DPFs) as well as for thermal management of other exhaust catalysts and components. For example, a DPF can become clogged over time, which decreases engine operating efficiency. These particulate filters can be regenerated to burn off the trapped particulate matter. The fuel fired burner is used to generate/increase heat such that the particulate matter can be burned off. Typically, the fuel delivery system of a fuel fired burner has an air flow and a fuel flow that provide a fuel/air mixture via a nozzle. An igniter ignites the fuel/air mixture sprayed from the nozzle to increase heat for regeneration or thermal management of aftertreatment.
In certain applications, an airless nozzle configuration is used instead of a fuel/air mixture configuration. An airless nozzle is desirable because this type of nozzle eliminates parasitic loss of compressed air, as well as eliminating the additional cost and complexity due to added components to supply air. In this type of configuration, the nozzle receives only a fuel supply and does not include a source of compressed air. Exhaust gas flows in an axial direction along the nozzle and mixes with fuel droplets sprayed from the nozzle. An igniter then ignites the mixture of exhaust gas and fuel droplets.
One concern with an airless nozzle is fuel coking within the nozzle as well as the associated fuel line if it is exposed to heat. During engine operation, the fuel can undergo chemical changes leading to the formation of carbon based dry materials that can plug the nozzle. This chemical degradation of the fuel is often referred to as fuel “coking.”